US3787629A - Apparatus for distinguishing between various fm broadcast multiplex transmissions - Google Patents

Apparatus for distinguishing between various fm broadcast multiplex transmissions Download PDF

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US3787629A
US3787629A US00251771A US3787629DA US3787629A US 3787629 A US3787629 A US 3787629A US 00251771 A US00251771 A US 00251771A US 3787629D A US3787629D A US 3787629DA US 3787629 A US3787629 A US 3787629A
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subcarrier
stereophonic
channel
signal
reception
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A Limberg
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RCA Licensing Corp
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RCA Corp
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04H—BROADCAST COMMUNICATION
    • H04H20/00—Arrangements for broadcast or for distribution combined with broadcast
    • H04H20/86—Arrangements characterised by the broadcast information itself
    • H04H20/88—Stereophonic broadcast systems
    • H04H20/89—Stereophonic broadcast systems using three or more audio channels, e.g. triphonic or quadraphonic

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  • Receiverlapparatus to detect the transmission of such a flag subcarrier comprises a threshold detector coupled by a subsonic low pass filter to the corresponding synchronous subchannel detector. Indicating and/or automatic switching apparatus responsive to the detector output is provided.
  • a multiplex signal termed a composite stereophonic signal is transmitted which comprises the additive combination of a main or sum signal including left plus right (L+R) loudspeaker signals in a frequency range extending from 50 to l,500I-Iz, a pilot signal at a frequency of l9kI-Iz, a stereophonic difference signal including left minus right (L-R) information impressed as double AM sidebands on a suppressed 38kHz stereophonic subcarrier, the latter subcarrier being in predetermined time relation with the pilot subcarrier and the sidebands extending over a frequency range of 23kI-Iz to 53kHz.
  • the multiplex signal may also include, besides the' composite stereophonic'signal components, an SCA subchannel in which a frequency modulated subcarrier (usually at 67kHz) is provided to transmit privileged information.
  • one proposal involves a quadrature subchannel having double AM sidebands impressed on a suppressed 38kHz subcarrier in quadrature (90) phasing with the stereophonic subcarrier. Additional subchannels, including information modulated on 57kHz or 76kHz subcarriers have also been'proposed.
  • the l9kHz pilot signal is used as a flag to distinguish transmission of stereophonic information from the transmission of monophonic or only main channel information.
  • the l9kI-Iz pilot signal is not only a flag for two channel stereophonic transmission but serves in the receiver as a timing reference for regenerating the suppressed 38kI-Iz subcarrier so as to permit demodulation of the (L-R) difference signal information.
  • the l9kI-Iz pilot signal and an L-R difference signal subchannel preferably are retained when surround stereophonic signals are transmitted so as not to interfere with the reception, by stereophonic receivers already in the field, of two channel information contained in these signals.
  • a transmission is of the conventional two channel type or of the surround stereophonic type for the following reasons.
  • the matrixing of the main channel and subchannel signals should be changed to accommodate differences in the aural perspective afforded by two channel and surround stereophonic reproductions.
  • detectors associated with unused in program selection To distinguish between two channel and surround stereophonic transmission it has been suggested that a flag signal accompany one of these two types of transmission.
  • thetransmitter equipment includes. a balanced, amplitude modulator for each subcarrier wave.
  • a balanced, amplitude modulator for each subcarrier wave.
  • the conventional difference signal (L-R) for two-channel stereophonic transmissions, one of the balanced modulators is excited by the conventional difference signal (L-R) while the other (the quadrature modulator) is not required for audio information transmission.
  • L-R conventional difference signal
  • the quadrature modulator the quadrature modulator
  • each of the balanced modulators is excited, .one by the (L-R) difference information and theother, for example, .by the difference between front and back (F-B) information.
  • one or more detectors required for surround stereophonic reproduction are unused during two channel stereophonic transmissions.
  • a system for generation and detection of a flag to indicate whether two channel or surround stereophonic sound is being transmitted is arranged toutilize available but unused apparatus in each of the transmitter and receiver.
  • Atleast-one of the balanced modulators (e.g., the quadrature modulator) at the transmitter is unbalanced during two channel transmissions by applying a direct potential to such modulator.
  • the conventional l9kI-Iz pilot signal distinguishes the two channel from monophonic transmission.
  • an appropriately phased tone generator operating at the fixed frequency may provide the flag, for example, where the transmitter is not equipped for transmission of the second subchannel (e.g'., a conventional two channel transmitter).
  • the admixture of 38kHz quadrature subcarrier with the two-channel composite stereophonic signal produces no direct signal in the stereophonic subchannel demodulators of receivers employing a synchronous detector for (L-R) detection, as is the case for most current receivers.
  • a direct signal will be produced in the quadrature subchannel detector during two-channel stereophonic broadcasting.
  • the absence or presence of this direct signal maythen be detected to determine which type of stereophonic transmission two-channel or surround is being received. Such determination permits appropriate indicator means to be activated and the detected multiplex signals to be appropriately matrixed for application to loudspeakers.
  • FIG. 1 illustrates, in block diagram form, a portion of a frequency modulation (FM) transmitter for broadcast of monophonic, two channel stereophonic or surround stereophonic sound information;
  • FM frequency modulation
  • FIG. 2 illustrates, in block diagram form, a surroundstereophonic FM receiver employing two separate subchannel detectors also being arranged for detection of information representative of presence or absence of surround-stereophonic information in the received signal; and p i FIG. 3 illustrates, in block diagram form, a surroundstereophonic FM receiver employing time-division multiplex demodulation and including apparatus for detecting presence or absence of surroundstereophonic information in the received signal.
  • three audio frequency signals are coupled to respective pre-emphasis net! works 20, 22 and 24.
  • the pre-emphasized sum signal e.g., the sum of front, back, left and right audio signals
  • the pre-emphasized stereophonic signal e.g., the difference between left and right audio signals
  • a second input is supplied to modulator 28 by a conventional synchronized oscillator such as the illustrated 38kI-Iz VCO (voltage controlled oscillator) 30 which is arranged to provide a continuous subcarrier wave at 38kHz.
  • Oscillator 30 is locked in phase and frequency with respect to a continuous wave l9kHz pilot tone provided by a crystal oscillator 32.
  • the output of l9kHz oscillator 32 is coupled to a first input of a synchronous phase detector 36 while the output of 38kHz oscillator 30 is coupled via. a frequency divider stage 34 to a second input of phase detector 36.
  • Detector 36 produces output signals representative of phase errors between oscillator 32 and the divided output of 38kHz oscillator 30 so as to correct the operating phase of oscillator. 30 in a well-known manner.
  • Balanced modulator 28 in response to the applied 38kl-lz subcarrier and the stereophonic difference signal, couples a double sideband amplitude modulated (AM) suppressed subcarrier signal to summing network 26.
  • AM double sideband amplitude modulated
  • the pre-emphasized quadrature signal components are applied to a second balanced modulator 38.
  • a second 38KI-Iz subcarrier wave in quadrature (90) phase relationship to the output of oscillator 30 is coupled to modulator 38.
  • the quadrature 38KHz wave is provided, for example, by means of a second 38KI-Iz voltage controlled oscillator 40 which is locked in phase with respect to oscillator 30 by means of a second synchronous phase detector 42.
  • Balanced modulator 38 in response to the applied quadrature 38Kl-lz subcarrier and the surround stereophonic difference signal, couples a double sideband amplitude modulated (AM) suppressed subcarrier signal to network 26.
  • the 19KHz pilot signal output of oscillator 32 is also coupled to summingnetwork 26 by .means of a switch 50 shown in the closed (NON MONO) position.
  • SCA signals privileged communication signals
  • SCA signals also may be applied to summing network 26.
  • the resultant composite signal output of network 26 is processed in a conventional manner forapplication to a frequency modulator 44, 'power amplifier 46' and antenna 48 for transmission.
  • the unbalancing means comprises a source of direct potential 52 which is coupled via a switching means 54, a subsonic (low-pass) filter 56 and a summing network 58 to quadrature modulator 38.
  • Switching means 54 is maintained in the open position during either surround stereophonic or monophonic signal transmission so that direct potential source 52' has no effect on the operation of modulator 38. However, when two channel stereophonic information is broadcast, switching means 54 is closed, thereby providing a direct potential to modulator 38 to cause it to operate in an unbalanced manner. That is, a 38KHz subcarrier component will'be present at the output of modulator 38.
  • the quadrature signal input to modulator 38 will be zero under two channeltransmission conditions so that an unmodulated 38KHZ flag subcarrier will be included in the composite signal output of network 26.
  • the simultaneous presence of 19KHz pilot and unmodulated 38KI-Iz quadrature subcarrier signals is then indicative of two channel stereophonic transmission.
  • the simultaneous absence of the 38KI-lz flag and presence of 19Kl-Iz pilot is indicative ,of surround stereophonic transmission and the absence of both l9KI-lz pilot and 38KI-Iz flag is indicative of monophonic transmission.
  • FM broadcast signals are intercepted by an antenna 101 and are applied to an FM tuner 103 comprising an R-F amplifier, a local oscillator, a mixer, I- -F amplifiers and'limiters and an FM detector arranged, for'producing at the output of the detector a composite signal which is a replica of the signal modulating the received FM R-F carrier.
  • an FM tuner 103 comprising an R-F amplifier, a local oscillator, a mixer, I- -F amplifiers and'limiters and an FM detector arranged, for'producing at the output of the detector a composite signal which is a replica of the signal modulating the received FM R-F carrier.
  • the composite, signal output of the detector portion of tuner 103 comprises a sum component extending over the audio frequency range (e.g.' 50 Hz to 15,000Hz), a continuous wave pilot component ata nominal frequency of l9kHz, a stereophonic difference signal component impressed as a first pair of AM side bands on a first suppressed 38kHz subcarrier, the sidebands extending between 23kHz and 53kHz, and a quadrature difference signal component impressed as a second pair of AM sidebands on a second suppressed 38kI-Iz subcarrier in quadrature relationship with the first subcarrier.
  • a sum component extending over the audio frequency range (e.g.' 50 Hz to 15,000Hz)
  • a continuous wave pilot component ata nominal frequency of l9kHz
  • a stereophonic difference signal component impressed as a first pair of AM side bands on a first suppressed 38kHz subcarrier
  • the sidebands extending between 23kHz and 53kHz
  • the first pair of sidebands are representative of the difference between left and right (L-R) audio signals while the second (quadrature) pair of sidebands are representative of the difference between front and back ('F'B) audio signals, the directions being specified with reference to a listeners position.
  • L-R left and right
  • 'F'B front and back
  • oscillator 105 means, illustrated as a 38kH'z oscillator 105, are provided for regenerating a 38kI-Iz subcarrier in the receiver.
  • the oscillator 105 is synchronized in frequency and phase by synchronization circuitry 107 responsive to the nominal 38kI-1z signal from the oscillator 105 and to a pilot signal component coupled from the FM tuner 103 by pilot signal separation circuitry 109. While oscillator 105 and associated automatic frequency and phase control apparatus are shown in FIG. 1 as the means for supplying a 38kI-Iz subcarrier, frequency doubling or injection-locked oscillator. arrangements, as are also known in the prior art, may alternatively be used without derogation of the present invention. An oscillator operating at a harmonic of 38kHz and associated frequency dividers alternatively may be used.
  • the synchronized 38kHz subcarrier is applied to a phase-shift network 111 to produce 38k1-1z stereophonic and quadrature subcarriers, which subcarriers are in fixed quadrature (90) phase relationship to eachother.
  • the stereophonic subcarrier as in a conventional two channel FM receiver, is the second harmonic of the l9kI-Iz pilot signal component of the detected composite signal and crosses an average value axis coincidentally with the pilot signal component.
  • the stereophonic subcarrier is applied together with the detected composite signal to a stereophonic subchannel detector 113 which demodulates L-R (and R-L) information in the detected composite signal.
  • quadrature 38k11z subcarrier from the phase-shift network ,1 11 is applied together with the detected composite signal to a quadrature subchannel detector 115 which demodulates the information contained in that subchannel of the detected composite signal.
  • the demodulated information may, for example, be front minus back (F-B) information and antiphase B-F information.
  • the F-B and B-F information from detector 115,, the L+R+F+B information contained in the 50-l5,000Hz portion of the detected composite signal and the L-R and R-L information provided by the detector 113 are additively matrixed together in various combinations at the inputs of deemphasis amplifiers 117, 119, 121, 123. Deemphasized and amplified audio signals are then supplied to respective loudspeakers 127, 12-9, 131 and 133 surrounding a listener 135.
  • the unmodulated quadrature 38k1-1z subcarrier is present in the received signals.
  • a direct signal component therefore is detected and is provided from the output circuit of the quadrature subchannel detector 115.
  • This direct signal (e.g. voltage) component is separated from the ultrasonic remnants of the detection process in a subaudio lowpass filter 137 which passes only subsonic frequencies (e.g., below 20112).
  • the output of filter 137 is supplied to a threshold detector 139 which senses the absence or presence of the direct signal component and provides electrical indications thereof.
  • These electrical indications are converted to audible or visible indications (or both if desired) by an appropriate transmission mode indicator 141.
  • indicator 141 may be alight-of the type frequently used for indications of two channel reception in conventional two channel stereophonic receivers.
  • gates 143 and 145 decouple the outputs of quadrature subchannel detector from the input circuits of the de-emphasis and matrixing amplifiers 117, 119, 121, 123, so the detected noise from the vacant subchannel is not included in the signals coupled to the loudspeakers 127, 129, 131, 133. This improves the signal-to-noise ratio of these signals during two-channel stereophonic reproduction.
  • additional gates 147 and 149 may be included, if desired, to decouple the signals normally provided by the de-emphasis amplifiers 119, 121 to the loudspeakers 129, 131, respectively.
  • gate 147 prevents L signals from being reproduced by left-rear loudspeaker 129 and such signals (L) are reproduced only by left-front loudspeaker 127. If gate 147 is omitted during two channel reception, the two-channel left (L) signal will appear in each of speakers 127 and 129, causing the soundv source to appear from the listeners left rather than the left-front quadrant, as is customary in two channel reproduction.
  • Gate 149 is arranged-to provide a similar function with respect to the two channel reproduction of right (R) signals. This switching preserves proper sound perspective despite the number of subchannels in the stereophonic broadcast, two-channel stereophonic L and R signals beingdesigned to reproduce sound sources spaced apart at extremes of the front quadrant, rather than in the spatial relationship of the L and R signals in surround stereophonic transmissions.
  • FIG. 3 shows a time-division multiplextype of FM radio receiver
  • the antenna 201, FM tuner 203, 38kHz oscillator 205, pilot and 38k1-1z oscillator synchronization circuitry 207, and pilot subcarrier separationcircuitry 209 correspond to elements 101, 103, 105, 107, 109 in the radio receiver diagrammed in FIG. 2.
  • the phase shift network 210 provides 38kI-1z subcarrier in +45, 1 35, +135 and 45 phases with respect to the stereophonic subchannel, which phases of subcarrier are respectively applied to left-front signal detector 212, right-rear signal detector 214, left-rear signal detector 216 and right-front signal, detector 218, respectively.
  • Each of these detectors 212, 214, 216, 218 samples the composite stereophonic signal supplied to it from the FM tuner 103;
  • the resultant decoded left-front (L,), right-rear (R leftrear (L and right-front (R signals from the detectors 212, 214, 216, 218, respectively are coupled to deemphasis and power amplifiers 222, 224,226, 228, respectively, and thence to loudspeakers 227, 231, 229 and 233, respectively.
  • the de-emphasis amplifiers222, 224 may be interconnected to provide greater differential mode again than common mode gain for L, and R, signals applied thereto to compensate for detection efficiency differences between main channel and subchannel sampling when wide-angle (e.g., 180) sampling is used.
  • the de-emphasis amplifiers 226, 228 may be similarly interconnected to provide greater differential mode than common mode gain for L, and R signals applied thereto to compensate for detection efficiency differences between main channel and subchannel sampling. 1
  • the accompanying quadrature subcarrier transmission flag will produce a direct component evidenced as a shift between the recovered direct signal in the leftfront and right-front detectors 212, 218 as compared to the left-rear and right-rear detectors 214, 216.
  • This shift will be evidenced as a direct voltage in the output circuit of a differential amplifier 230 having its inverting and non-inverting input circuits separately and respectively connected to one of the front detectors (212 or 218) and one of the rear detectors (214 or 216).
  • the output signal from the differential amplifier 230 is filtered in a sub-audio low-pass filter 237 and applied to a threshold detector 239, which senses the absence or presence of the direct voltage (or current) and provides electrical indications thereof.
  • transmission mode indicator circuitry 241 may be used to de-couple signals from the rear loudspeakers 229, 231 during two-channel stereophonic reception by means of gates 232 and 234.
  • Gates 232 and 234 are rendered transmissive during two-channel stereophonic signal reception to add signal originating from the left-rear detector to that originating from the left-front detector in an additive matrix 236 and to add signal originating from the right-rear detector to that originating from the right-front detector in an additive matrix 238.
  • the signals add constructively while the noise contribution of the quadrature subchannel being anti-phase in the added signals is cancelled. An improvement in two-channel stereophonic signal reproduction is thus obtained.
  • FIGS. 1 and 2 Certain variations of the basic schemes shown in FIGS. 1 and 2 are contemplated in the present invention. Gating to decouple loudspeakers from the quadrature subchannel information or to decouple them from application of signal can be effectuated prior to de-' emphasis as well as thereafter.
  • the use of a differential amplifier to eliminate common-mode direct bias in multiplex detector outputs prior to subsonic filtering and threshold detection to sense presence or absence of 38ltHz flag subcarrier can be applied to a matrix receiver of the type shown in FIG. 1.
  • a composite signal including, during two channel stereophonic reception, an audio sum signal component, a continuous wave pilot signal component at a predetermined frequency, a stereophonic audio difference signal component impressed as a'first pair of amplitude modulation sidebands on a first suppressed subcarrier, the subcarrier being at the second harmonicfrequency of said pilot signal and in predetermined time relationship therewith, and an unmodulated subcarrier at a frequency equal to said suppressed subcarrier and in quadrature phase relationship therewith, said composite signal further including, during surround stereophonic reception, a surround stereophonic audio difference signal component impressed as a second pair of amplitude modulation sidebands on a second suppressed subcarrier, the second subcarrier being at the same frequency and phase as said unmodulated subcarrier and being substituted for said unmodulated subcarrier, synchronous detection means, coupled to said composite signal providing means, responsive during two channel reception to said unmodulated subcarrier and responsive during surround stereophonic reception to said sidebands'associated with said second suppresse
  • a composite signal including an audio sum signal component, a continuous wave pilot signal component ata predetermined fre quency, a stereophonic audio difference signal 7 component impressed as a first pair of amplitude modulation sidebands on a first suppressed subcarrier, the subcarrier being at the second harmonic frequency of said pilot signal and in predetermined time relationship therewith, and an unmodulated subcarrier at a frequency equal tosaid suppressed subcarrier but in quadrature phase relationship therewith, and I means for substituting for'said unmodulated subcarrier, during surround stereophonic transmission, an additional composite signal component including surround stereophonic audio difference signals impressed as a second pair of amplitude modulation sidebands on a second suppressed subcarrier, the second subcarrier being at the same frequency and relative phase with respect to saidfirst subcarrier as said unmodulated subcarrier.
  • an FM broadcast system apparatus for providing transmission-mode distinguishing information as claimed in claim 2 including 7 i a balanced modulator having a first input circuit for application of subcarrier, having a second input circuit for application of modulating signal and having an output circuit to provide at least a portion of said second pair of amplitude modulation sidebands;
  • a source of direct signal and switching means to couple said source of direct signal to said second input circuit of said balanced modulator during the transmission of two channel stereophonic sound signals.
  • gating means rendered non-transmissive in the absence of said indication of two channel reception
  • I combining means to combine signals coupled thereto from said synchronous detection means responsive to said first pair of amplitude modulation sidebands and signals coupled thereto via said gating means from said synchronous detection means responsive to said second pair of amplitude modulation sidebands.

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US00251771A 1972-05-09 1972-05-09 Apparatus for distinguishing between various fm broadcast multiplex transmissions Expired - Lifetime US3787629A (en)

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Cited By (16)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3881063A (en) * 1972-01-20 1975-04-29 Victor Company Of Japan System for selectively receiving either 4-channel or- 2-channel stereophonic broadcastings
US3902018A (en) * 1973-12-03 1975-08-26 Zenith Radio Corp Multiple channel fm stereo system employing am vestigial sideband subcarrier modulation
US3904828A (en) * 1972-04-25 1975-09-09 Siemens Ag Compatible system for transmitting and receiving quadraphonic signals
US3940559A (en) * 1974-04-18 1976-02-24 Cbs Inc. Compatible four channel recording and reproducing system
US3944747A (en) * 1972-08-24 1976-03-16 Zenith Radio Corporation Multiple channel FM stereo system
US3961276A (en) * 1974-06-27 1976-06-01 Sansui Electric Co., Ltd. Stereo signal demodulator in a four-channel stereo broadcast receiver comprising means for performing delay equalization together with sampling of a composite signal
US3980832A (en) * 1974-02-25 1976-09-14 Sony Corporation Decoder for four channel FM stereophonic composite signal having an Indicating signal wherein the indicating signal is detected and used in the decoding of the four channel composite signal
US4013841A (en) * 1971-12-23 1977-03-22 Matsushita Electric Industrial Co., Ltd. Four-channel stereo receiver
US4027107A (en) * 1973-09-28 1977-05-31 Zenith Radio Corporation Multiple channel FM stereo system
US4564867A (en) * 1980-07-24 1986-01-14 Universal Pioneer Corporation Video disc recording and reproducing device for video discs having recognition signal indicative of content of associated program signal
US4821322A (en) * 1987-08-12 1989-04-11 Bose Corporation FM multiplex decoding
US5155770A (en) * 1990-09-17 1992-10-13 Sony Corporation Surround processor for audio signal
US5412731A (en) * 1982-11-08 1995-05-02 Desper Products, Inc. Automatic stereophonic manipulation system and apparatus for image enhancement
US20020006205A1 (en) * 1999-11-16 2002-01-17 Vincent Lam Man Tai Method and apparatus for high fidelity wireless stereophonic transmission utilizing dual frequency carriers
EP0836365A3 (en) * 1996-10-11 2003-01-22 Victor Company of Japan, Ltd. System for processing audio surround signal
US7149312B1 (en) * 1999-10-20 2006-12-12 Sony Deutschland Gmbh Method and device to retrieve RDS information

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JPS5113208U (ko) * 1974-07-17 1976-01-30

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US1941067A (en) * 1932-10-20 1933-12-26 Edwin H Armstrong Radio broadcasting and receiving
GB1059007A (en) * 1965-11-25 1967-02-15 Telefunken Patent Improvements relating to stereophonic radio receivers
US3679832A (en) * 1971-03-23 1972-07-25 Bell Telephone Labor Inc Three-channel fm stereo transmission
US3708623A (en) * 1970-04-29 1973-01-02 Quadracast Syst Inc Compatible four channel fm system

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CA969240A (en) * 1971-04-15 1975-06-10 Sukeichi Miki Four channel fm transmitter, receiver and transmission system

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US1941067A (en) * 1932-10-20 1933-12-26 Edwin H Armstrong Radio broadcasting and receiving
GB1059007A (en) * 1965-11-25 1967-02-15 Telefunken Patent Improvements relating to stereophonic radio receivers
US3708623A (en) * 1970-04-29 1973-01-02 Quadracast Syst Inc Compatible four channel fm system
US3679832A (en) * 1971-03-23 1972-07-25 Bell Telephone Labor Inc Three-channel fm stereo transmission

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Cited By (17)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4013841A (en) * 1971-12-23 1977-03-22 Matsushita Electric Industrial Co., Ltd. Four-channel stereo receiver
US3881063A (en) * 1972-01-20 1975-04-29 Victor Company Of Japan System for selectively receiving either 4-channel or- 2-channel stereophonic broadcastings
US3904828A (en) * 1972-04-25 1975-09-09 Siemens Ag Compatible system for transmitting and receiving quadraphonic signals
US3944747A (en) * 1972-08-24 1976-03-16 Zenith Radio Corporation Multiple channel FM stereo system
US4027107A (en) * 1973-09-28 1977-05-31 Zenith Radio Corporation Multiple channel FM stereo system
US3902018A (en) * 1973-12-03 1975-08-26 Zenith Radio Corp Multiple channel fm stereo system employing am vestigial sideband subcarrier modulation
US3980832A (en) * 1974-02-25 1976-09-14 Sony Corporation Decoder for four channel FM stereophonic composite signal having an Indicating signal wherein the indicating signal is detected and used in the decoding of the four channel composite signal
US3940559A (en) * 1974-04-18 1976-02-24 Cbs Inc. Compatible four channel recording and reproducing system
US3961276A (en) * 1974-06-27 1976-06-01 Sansui Electric Co., Ltd. Stereo signal demodulator in a four-channel stereo broadcast receiver comprising means for performing delay equalization together with sampling of a composite signal
US4564867A (en) * 1980-07-24 1986-01-14 Universal Pioneer Corporation Video disc recording and reproducing device for video discs having recognition signal indicative of content of associated program signal
US5412731A (en) * 1982-11-08 1995-05-02 Desper Products, Inc. Automatic stereophonic manipulation system and apparatus for image enhancement
US4821322A (en) * 1987-08-12 1989-04-11 Bose Corporation FM multiplex decoding
US5155770A (en) * 1990-09-17 1992-10-13 Sony Corporation Surround processor for audio signal
EP0836365A3 (en) * 1996-10-11 2003-01-22 Victor Company of Japan, Ltd. System for processing audio surround signal
US7149312B1 (en) * 1999-10-20 2006-12-12 Sony Deutschland Gmbh Method and device to retrieve RDS information
US20020006205A1 (en) * 1999-11-16 2002-01-17 Vincent Lam Man Tai Method and apparatus for high fidelity wireless stereophonic transmission utilizing dual frequency carriers
US7343015B2 (en) * 1999-11-16 2008-03-11 Radio Shack Corporation Method and apparatus for high fidelity wireless stereophonic transmission utilizing dual frequency carriers

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JPS4949505A (ko) 1974-05-14
DE2323461C3 (de) 1981-01-15
FR2183975B1 (ko) 1978-09-29
CA1000797A (en) 1976-11-30
AU467834B2 (en) 1975-12-11
NL7306405A (ko) 1973-11-13
IT984181B (it) 1974-11-20
DE2323461B2 (de) 1980-05-14
ES414568A1 (es) 1976-02-01
AU5516973A (en) 1974-11-07
DE2323461A1 (de) 1973-11-29
FR2183975A1 (ko) 1973-12-21
JPS5325601B2 (ko) 1978-07-27
GB1416627A (en) 1975-12-03

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